A hemodialysis treatment is a treatment in which the blood of a patient is extracorporeally circulated to purify the blood. In such hemodialysis treatment, a dialysis device and a dialyzer as a blood purifier that allows dialysate to flow are used, and a blood circuit, which causes the blood of a patient to be extracorporeally circulated, is connected to the dialyzer, the blood and dialysate are brought into contact with each other via a semipermeable membrane of the dialyzer, and the waste and excess water in the blood can be removed (removal of excess water is referred to as “ultrafiltration”). A configuration is adopted in which the blood purified by the dialyzer is returned to the body of the patient via a puncture needle, whereas the waste and excess water are discharged to the outside along with the dialysate.
The dialysis device has a dialysate introduction line through which dialysate is introduced into the dialyzer, and a dialysate discharge line through which the dialysate introduced into the dialyzer is discharged along with the waste and excess water, and coupling tools (coupling) which can be coupled to the dialyzer are respectively attached to the leading end of the dialysate introduction line and the leading end of the dialysate discharge line. These coupling tools are configured to form a closed circuit with the dialysate introduction line and the dialysate discharge line by connecting to each other when treatment is not made, and when treatment is started (or when preparation for dialysis is made), the connection is released, and thus the coupling tools each can be coupled to the dialyzer (for instance, see PTL 1).